One type of common orthodontic treatment involves the use of a set of tiny appliances commonly known as brackets and buccal tubes. Buccal tubes are normally mounted on the molars and brackets are attached to all other teeth. Each bracket is secured to a corresponding tooth through a bonding adhesive which is sandwiched between the pad of bracket on one side and enamel surface of the tooth on the other side. Each bracket has a slot to receive a resilient archwire. The slot forms a track to guide movement of the teeth to desired positions. Ends of archwire are commonly placed in slots or channels of buccal tube appliances that are attached to the molar teeth either through bonding with adhesive or first welded on a band and then cemented on the tooth.
Use of Brackets on Deciduous Teeth
Up to the present time, the orthodontic brackets and tubes (braces) which are available in the market have been designed for permanent teeth. Several forms of bite problems (malocclusion) develop during childhood in the deciduous (primary) dentition. Most common amongst them are cross bites of the anterior or posterior teeth. The advances in our understanding of children growth and development and in interceptive orthodontics have made the treatment of younger children more desirable.
Such treatment is done during the deciduous (primary) dentition or during mixed-dentition period when the deciduous teeth are still present. There are circumstances that early correction of a malocclusion during deciduous or mixed-dentition periods would either prevent or reduce the extent of treatment at a later date.
Deciduous teeth can be moved to allow better jaw relationship, to make room for the permanent teeth or used as anchors for more efficient movement of the permanent teeth. Malocclusions that involve deciduous teeth are simpler and easier to correct that malocclusion of permanent teeth. This is due to the younger age of the patients for whom the tissues surrounding deciduous teeth are more adaptive and allow faster movement of the deciduous teeth with smaller increments of force.
Due to a lack of availability of brackets and tubes for the deciduous teeth, the orthodontists are forced to either defer the treatment to allow the development of permanent dentition or use the appliances that are designed for permanent teeth and place them on the deciduous teeth. Due to different size and shape of these teeth the permanent teeth bracket bases do not adapt well to the deciduous teeth surfaces. Further, studies performed in Japan (American Journal of Orthodontics and Dentofacial Orthopedics Vol. 134/2008 pp. 198-208 article—“Comparison of shear bond strengths of orthodontic brackets bonded to deciduous and permanent teeth” by Endo, T. et. al.) have shown that permanent brackets bond more weakly to deciduous as opposed to permanent teeth. The researchers attributed the weak bonding to a difference in the chemical structure of the enamel found on deciduous teeth as compared to permanent teeth. As a result of these and other factors, brackets bonded to deciduous teeth frequently come loose during the course of treatment creating inconvenience and frustration for both the patient and the dentist.
Additionally, the mode and rate of movement of deciduous teeth is different from permanent teeth. The brackets that are designed for permanent teeth are too large for the deciduous teeth therefore interfere with proper brushing, cause impingement of the gum tissues and apply several unnecessary force vectors on the deciduous teeth.
Debonding
Debonding brackets from deciduous teeth may also be a problem. Deciduous teeth become progressively looser prior to falling out due to the resorption of their roots. Therefore they may not have the structural integrity to easily sustain the pressure required for removal of a bracket as would a permanent tooth.
Metal brackets are commonly debonded using a plier-type hand instrument. Force is typically applied in the mesial-distal or diagonal direction causing deformation in the ductile bracket body. This deformation effects a separation or fracture at the interface between the bonding adhesive and the bracket base allowing the bracket to be peeled or pried away from the tooth surface.